Color cathode ray tubes has a panel on which triads of phosphors are formed; a funnel which is joined to the panel and is provided with a deflection yoke placed on the funnel's periphery; and a neck which is extended from the funnel and in which an electron gun for emitting electron beams is inserted.
A shadow mask through which the electron beams may pass and be scanned on each phosphor is placed at the inside of a skirt of the panel. This mask can be fixed by a means such as a mask frame. The mask frame is suspended by interposing a hook spring H between a stud pin S placed in panel P as shown in FIG. 3.
This shadow mask is fixed by the mask frame, being joined to its skirt part of the panel by the mask frame at the position where their minute apertures formed on the hole part thereof correspond to the phosphors layered on the inner surface thereof. However, this structure has a disadvantage of reducing color purity. That is, there is no mechanism to damp vibrations generated by external impact or speaker howling. This, due to these vibrations, the apertures formed at the outer surface of the shadow mask supported by the mask frame each do not properly align with the phosphors formed at the inner surface of the plate, so that the electron beams will impact off line thereon which reduces color purity.
To solve this problem, U.S. Pat. No. 3,638,063, issued to Takuji Tachikawa et al on Jan. 25, 1972, proposes a method that a damping wire or a damping rod is installed across a grid member of a CRT, so that the damping rod presses the grid member to prevent vibrations by external impact or other possible impacts.
U.S. Pat. No. 4,504,764 issued to Yasuhiro Sakamoto on Mar. 12, 1985, describes a method for reducing vibrations such that sonorous vibrations marks the sonorous frequency of a grill member of color selecting apertures.
However, the inventor has found that the above-mentioned solutions are not effective when strong vibrations exist, such as can be generated by external impact.